A philosophical zombie or p-zombie in the philosophy of mind and perception is a hypothetical being that is indistinguishable from a normal human being except in that it lacks conscious experience, qualia, or sentience. When a zombie is poked with a sharp object, for example, it does not feel any pain though it behaves exactly as if it does feel pain (it may say “ouch” and recoil from the stimulus, or tell us that it is in intense pain).

The notion of a philosophical zombie is used mainly in thought experiments intended to support arguments (often called zombie arguments) against forms of physicalism such as materialism, behaviorism and functionalism. Physicalism is the idea that all aspects of human nature can be explained by physical means: specifically, all aspects of human nature and perception can be explained from a neurobiological standpoint. Since a zombie is physiologically indistinguishable from human beings its hypothetical possibility is an argument for a consciousness that is more than the sum of neurological pathways and brain states.

from another thread:

isaac - 24 May 2011 10:43 AM

GdB - 23 May 2011 07:11 AM

isaac - 22 May 2011 02:01 PM

Hmm… obviously, such a zombie would NOT be physiologically identical to (even if it were indistinguishable from) a person with conscious experience.

In which case it is not a philosophical zombie anymore…

If we take the idea of zombies seriously, we must accept that 2 zombies in a philosophical discussion talk about their epiphenomena: in the end, they behave exactly like we do.

so there goes that whole argument, i would think

Yep. We can strike p-zombies and epiphenomena (in this context!) from our vocabulary.

i think we discounted them in two different ways. You seem to be saying that it’s pragmatically meaningless, even if logically possible—which i agree with—but i was saying that the concept is logically impossible, which i couldn’t tell if you agreed with or not.

Maybe i should just say that it’s logically impossible within the nature of “this world”, which would be ‘nomological impossibility’, i suppose? I suspect that it’s impossible in any physical world—which i think makes it “metaphysically impossible”?

again, wikipedia:

Logical possibility is usually considered the broadest sort of possibility; a proposition is said to be logically possible if there is no logical contradiction involved in its being true. “Dick Cheney is a bachelor” is logically possible, though in fact false; most philosophers have thought that statements like “If I flap my arms very hard, I will fly” are logically possible, although they are nomologically impossible. “Dick Cheney is a married bachelor,” on the other hand, is logically impossible; anyone who is a bachelor is therefore not married, so the sentence involves a logical contradiction.

Metaphysical possibility is either equivalent to logical possibility or narrower than it (what a philosopher thinks the relationship between the two is depends, in part, on the philosopher’s view of logic). Some philosophers have held that discovered identities such as Kripke’s “Water is H2O” are metaphysically necessary but not logically necessary (they would claim that there is no formal contradiction involved in “Water is not H2O” even though it turns out to be metaphysically impossible).

Nomological possibility is possibility under the actual laws of nature. Most philosophers since David Hume have held that the laws of nature are metaphysically contingent—that there could have been different natural laws than the ones that actually obtain. If so, then it would not be logically or metaphysically impossible, for example, for you to travel to Alpha Centauri in one day; it would just have to be the case that you could travel faster than the speed of light. But of course there is an important sense in which this is not possible; given that the laws of nature are what they are, there is no way that you could do it. (Some philosophers, such as Sydney Shoemaker[citation needed], have argued that natural laws are in fact necessary, not contingent; if so, then nomological possibility is equivalent to metaphysical possibility.)

note: i left out “temporal” and “historical” possibility because i don’t think they’re pertinent to this specific discussion. I do hope to start a thread on them later. Historical possiblility is especially interesting to me, and i think subdivides into many, many, meaningful sub-types; but lets not talk about that here.

Per definition, they cannot be distinguished from conscious agents: they have the same physiology and behave exactly the same. This means they will also discuss about their epiphenominal conscious states, even if they have none. If they would not do that (e.g. react on us with “what the hell are you talking about, I have no consciousness!”), they could be distinguished, which contradicts the very definition of p-zombies.

I call it logical impossible because the question of their existence can be answered without empirical research. I do have to know of course what conscious beings are, but that is the same as with “Dick Cheney is a married bachelor”. I don’t need a researcher (private detective in this case…) to now he is not a married bachelor. However, I must know what marriage is to see the contradiction.

Per definition, they cannot be distinguished from conscious agents: they have the same physiology and behave exactly the same. This means they will also discuss about their epiphenominal conscious states, even if they have none. If they would not do that (e.g. react on us with “what the hell are you talking about, I have no consciousness!”), they could be distinguished, which contradicts the very definition of p-zombies.

Why would something need to have consciousness in order to act like they are conscious?

The zombie argument is a version of general modal arguments against physicalism such as that of Saul Kripke against that kind of physicalism known as type-identity theory. Further such arguments were notably advanced in the 1970s by Thomas Nagel (1970; 1974) and Robert Kirk (1974) but the general argument was most famously developed in detail by David Chalmers in The Conscious Mind (1996). According to Chalmers one can coherently conceive of an entire zombie world, a world physically indistinguishable from this world but entirely lacking conscious experience. The counterpart of every conscious being in our world would be a p-zombie. Since such a world is conceivable, Chalmers claims, it is logically possible, which is all the argument requires.

Fundamental chasms in philosophy wrt to the zombie argument:

The zombie argument is difficult to assess because it brings to light fundamental disagreements about the method and scope of philosophy itself and the nature and abilities of conceptual analysis. Proponents of the zombie argument may think that conceptual analysis is a central part of (if not the only part of) philosophy and that it certainly can do a great deal of philosophical work. However others, such as Dennett, Paul Churchland and W.V.O. Quine, have fundamentally different views. For this reason, discussion of the zombie argument remains vigorous in philosophy.

Why would something need to have consciousness in order to act like they are conscious?

Just realise that the p-zombie cannot be distinguished from a normal human agent at all. Of course one can make programs that in a limited area act as if they are conscious, and I fully agree that those do not necessarily are conscious. But a p-zombie does not just pass the Turing test, it asks you about the meaning of life, wonders what consciousness is, wonders if you see a red rose as I do, is hurt by a stupid remark of mine, and we enjoy a nice night together… And in a medical checkup nothing special is found: her blood values are OK, the EEC shows nothing special, possibly the pain is psychosomatic… No difference at all, we defined, didn’t we?

We are not discussing ‘something’ we are discussing p-zombies.

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GdB

When the word ‘truth’ is uttered a shadow of violence is cast as well.

Since such a world is conceivable, Chalmers claims, it is logically possible, which is all the argument requires.

Is Chalmers really so naive?

Compare his argumentation:

1. According to physicalism all that exists in our world (including consciousness) is physical.
2. Thus, if physicalism is true, a logically-possible world in which all physical facts are the same as those of the actual world must contain everything that exists in our actual world. In particular conscious experience must exist in such a possible world.
3. In fact we can conceive of a world physically indistinguishable from our world but in which there is no consciousness (a zombie world) and we can not see why it is not logically possible.
4. Therefore, physicalism is false. (The conclusion follows from 2. and 3. by modus tollens.)

With Descartes’ version of the ontological proof of god’s existence:

1. Whatever I clearly and distinctly perceive to be contained in the idea of something is true of that thing.
2. I clearly and distinctly perceive that necessary existence is contained in the idea of God.
3. Therefore, God exists.

Is this meaning of ‘perceiving’ or ‘conceiving’ philosophically relevant?

1. Whatever I clearly and distinctly perceive to be contained in the idea of something is true of that thing.
2. I clearly and distinctly perceive a biggest number
3. Therefore, a biggest number exists.

Is this meaning of ‘perceiving’ or ‘conceiving’ philosophically relevant?

The meanings of perceive and conceive are not synonymous.

Perceive: to become aware or conscious through the senses

Conceive: devise in the mind, imagine

(Compact Oxford English Dictionary)

Certainly, they are distinct and philosophically relevant.

Thanks for the english.

But I did not ask for the distinction: but I ask, very precise now: what is the philosophical relevance of the fact that I can conceive of a world physically indistinguishable from our world but in which there is no consciousness (a zombie world)? What relevant do I say when I conceive of a unicorn? Is that relevant?

If Chalmers says he can conceive zombies, he did not really conceive it: he just fantasised it. To cite myself:

A p-zombie does not just pass the Turing test, it asks you about the meaning of life, wonders what consciousness is, wonders if you see a red rose as I do, is hurt by a stupid remark of mine, and we enjoy a nice night together… And in a medical checkup nothing special is found: her blood values are OK, the EEC shows nothing special, possibly the pain is psychosomatic… No difference at all, we defined, didn’t we?

If you say you conceive of such a zombie, I just say: you are lying. You did not think through everything a p-zombie would be. If I say to you “I conceive of a perfect circle with 3 corners”, wouldn’t you be sure I am lying? If I say I conceive of a thing that looks like a cat, it moves like a cat, behaves like a cat, feels like a cat, has the same organs as a cat made of the same substances, but it doesn’t live: wouldn’t you say I am lying?

But I did not ask for the distinction: but I ask, very precise now: what is the philosophical relevance of the fact that I can conceive of a world physically indistinguishable from our world but in which there is no consciousness (a zombie world)? What relevant do I say when I conceive of a unicorn? Is that relevant?

It is conceivable unlike unicorns which are mythical creatures.

If Chalmers says he can conceive zombies, he did not really conceive it: he just fantasised it.

From the same wiki on philosophical zombies:

Chalmers states: “Zombies are probably not naturally possible: they probably cannot exist in our world, with its laws of nature.”

But, that does not mean it is inconceivable.

If you say you conceive of such a zombie, I just say: you are lying. You did not think through everything a p-zombie would be. If I say to you “I conceive of a perfect circle with 3 corners”, wouldn’t you be sure I am lying? If I say I conceive of a thing that looks like a cat, it moves like a cat, behaves like a cat, feels like a cat, has the same organs as a cat made of the same substances, but it doesn’t live: wouldn’t you say I am lying?

Lying? Certainly not. Your example of the perfect circle with 3 corners is a contradiction in terms and is it not conceivable that a robotic cat can be so?

Chalmers states: “Zombies are probably not naturally possible: they probably cannot exist in our world, with its laws of nature.”

But, that does not mean it is inconceivable.

Yes, it does. “Behaves the same, same substance, not distinguishable from conscious agents”. That would be in any world that has natural laws. Chalmers seems also to believe in this ‘panexperientialism’ of sixfootbrit…

kkwan - 29 May 2011 12:13 AM

Lying? Certainly not. Your example of the perfect circle with 3 corners is a contradiction in terms and is it not conceivable that a robotic cat can be so?

Of course I would be lying: because you know it is a contradiction in terms. As you cannot separate a ‘robotic’ (your term!) not from a normal one, how could I even say it is robotic? It is an empty concept.

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GdB

When the word ‘truth’ is uttered a shadow of violence is cast as well.

Just realise that the p-zombie cannot be distinguished from a normal human agent at all. Of course one can make programs that in a limited area act as if they are conscious, and I fully agree that those do not necessarily are conscious. But a p-zombie does not just pass the Turing test, it asks you about the meaning of life, wonders what consciousness is, wonders if you see a red rose as I do, is hurt by a stupid remark of mine, and we enjoy a nice night together…

No, a p-zombie would not. By definition, there is nothing there to experience thoughts and emotions.

GdB, let me ask you this:
Do you know with absolute certainty that other minds exist?

Lying? Certainly not. Your example of the perfect circle with 3 corners is a contradiction in terms…

Of course I would be lying: because you know it is a contradiction in terms.

If you said you had a three-pointed circle, you’d be lying, because you know better. If i said i could conceive of non-physical substances, i’d either be lying or refering to the possibility that i could define “physical” as “detectable by the senses” or “as opposed to mental” or something… which i wouldn’t normally do.

And if i said that it’s logically possible, to me, that the earth could be larger than the sun… wouldn’t i have to be willfully narrowing my definitions of “earth” and “sun” for that to be “logically possible”?

Anyway, “to” someone who doesn’t know better—in this case, the proper full definitions of earth and sun—it would “be” logically possible, right?

If i’ve got those things right—maybe i don’t?—then all logical possiblities become either epistemic or metaphysical, no?

Subjunctive possibility (also called alethic possibility or metaphysical possibility) is the form of modality most frequently studied in modal logic. Subjunctive possibilities are the sorts of possibilities we consider when we conceive of counterfactual situations; subjunctive modalities are modalities that bear on whether a statement might have been or could be true—such as might, could, must, possibly, necessarily, contingently, essentially, accidentally, and so on. Subjunctive possibilities include logical possibility, metaphysical possibility, nomological possibility, and temporal possibility.

The contrast with epistemic possibility is especially important to draw, since in ordinary language the same phrases (“it’s possible,” “it can’t be”, “it must be”) are often used to express either sort of possibility. But they are not the same.

Just realise that the p-zombie cannot be distinguished from a normal human agent at all. Of course one can make programs that in a limited area act as if they are conscious, and I fully agree that those do not necessarily are conscious. But a p-zombie does not just pass the Turing test, it asks you about the meaning of life, wonders what consciousness is, wonders if you see a red rose as I do, is hurt by a stupid remark of mine, and we enjoy a nice night together…

No, a p-zombie would not. By definition, there is nothing there to experience thoughts and emotions.

?? A p-zombie would not what? Again: the definition of a p-zombie is that it behaves exactly the same as conscious agents. So if I talk about ‘red qualia’, or ‘what it looks like’ and she does not understand what I say, I have a criterion for it being a p-zombie.

Mingy Jongo - 29 May 2011 01:24 PM

Do you know with absolute certainty that other minds exist?

No, not absolutely sure, in the methodological exact sense. My wife could be a p-zombie, my children too. And I must confess that I will not be able to convince somebody else from the fact I am not a p-zombie. How could I? A GdB-p-zombie would say exactly the same as I do, per definition. But then, one might wonder why I talk about feelings when I do not have them…

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GdB

When the word ‘truth’ is uttered a shadow of violence is cast as well.

If you said you had a three-pointed circle, you’d be lying, because you know better.

Yes, I know better. Understanding the concepts of circles implicitly means knowing that it has no edges.

isaac - 29 May 2011 04:43 PM

And if i said that it’s logically possible, to me, that the earth could be larger than the sun… wouldn’t i have to be willfully narrowing my definitions of “earth” and “sun” for that to be “logically possible”?

If you don’t know anything about the earth and the sun, then it seems possible, yes. But if I narrow my definitions to stars and planets, then I see that at the moment I see that the sun is star, and the earth a planet of the sun, then it is logically impossible. Conceptually, a star does not orbit round a planet, per definition.

And now you should be able to see why I think that p-zombies are logically impossible. P-Zombies only exist as a concept: I have no examples of some human beings that turn out to be p-zombies, and some others who are conscious agents. I do not discover such facts as we did with the sun and the earth. I just created the concept of it. But it should be immediately clear that there is no way of distinguishing zombies from conscious agents, because they behave exactly the same. So can I honestly say I can ‘conceive of a world physically indistinguishable from our world but in which there is no consciousness’? I say you can’t because you cannot see the difference between such a world and ours. You defined it that way.

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GdB

When the word ‘truth’ is uttered a shadow of violence is cast as well.